Indian Journal of Plant Physiology

The present study deals with the impact of simulated water stress on the physiology of leaf senescence in three genotypes of cowpea (Vigna unguiculata), viz. Akshay-102(A), Gomti vu-89(G) and Pusa Falguni(P). The induced water stress created by withholding water supply from flowering stage causes significant declines in the levels of chlorophylls with an increase in the amount of total carotenoids during senescence of the leaves of all the three presently studied genotypes of cowpea plants in comparison to that of control plants. A significant decrease in the amount of total protein is associated with the significant increase in the net pool of total free amino acids in Pusa Falguni and Gomti genotype during maturation and senescence stage of leaves. The increase in the levels of total phenols occur consistently, but significant increase occurs only at 65 and 75 days in Pusa Falguni and Akshay, while in Gomti it occurs from 55 to 75 days age of plants. The levels of nucleic acids (DNA and RNA) declined during maturation and senescent stage of leaves, but only Akshay exhibits non-significant decrease in the levels of its RNA. The specific activity of acid and alkaline proteases are more during the maturation and senescence of leaves in plants facing induced water stress condition than that of plants grown in the control plot, but this activity is found to be significant only in Gomti variety. While the specific activity of catalase decreases, that of peroxidase and polyphenoloxidase increases during development, maturation and senescence of leaves in all three genotypes. From the obtained data, it may be concluded that Akshay genotype displayed better drought tolerance than other two genotypes of cowpea.